Infection with the human immunodeficiency virus (HIV), and its terminal clinical stage, acquired immunodeficiency syndrome (AIDS), were first described in homosexual males. Subsequently, a second major risk group for HIV infection consisting of intravenous drug users (IVDU) was identified. Among the important clinical manifestations of HIV disease is the occurrence of unusual oral lesions. The frequency and distribution of these lesions were originally described in homosexual males with AIDS. Oral manifestations of HIV infection may be an early clinical sign of disease progression, but the significance of these lesions to other aspects of HIV disease have not been defined. Two broad questions concerning the oral manifestations of HIV infection can be posed: 1. What differences exist in the occurrence of oral manifestations of HIV disease if different risk groups and 2. What is the temporal relationship of development of HIV infection and its accompanying immunodeficiency to the development of both oral and systemic manifestations of the disease. This Program Project will address these issues by longitudinally studying patients being monitored by the HIV Center for Clinical and Behavioral Studies at the Psychiatric Institute/Columbia Presbyterian Medical Center. This Center studies a large cohort of homosexual males, male IVDU and female IVDU. All patients are either seronegative or seropositive, and have not progressed to clinical AIDS. These patients will receive an intraoral examination at each of their 6 month medical evaluations. Oral findings will be correlated with the immunologic and systemic changes that characterizes the development of HIV disease. In addition, this Program Project will comprehensively study host-microbial interaction as a function of developing immunodeficiency. Evaluating a subcohort of patients, the clinical progression of periodontal disease will be correlated with infection of the subgingival environment and the local and systemic host response. The Core section of this Program Project will provide the administrative logistical and statistical support to allow the studies to be performed.